This application pertains to the art of mirrors of concave configuration. It is well known that in constructing concave mirrors having large focal lengths it is important to avoid defects which may vary the focal point of the mirror. This consideration may be particularly acute in large focal length mirrors, such as those used for collection of solar energy, where the mirror is constructed of a large number of concave mirrors, each of which must have a relatively precise and tight focus so that a large majority of the rays striking the mirror will be reflected at a common focal point.
It has also been recognized that it has been heretofore difficult to mechanically deform a rigid mirror into a precise concave shape and maintain it in that concave shape without it having defects which might vary the focal point the mirror. This problem is particularly prevalent in constructing paraboloid shaped mirrors. Consequently, in constructing concave mirrors, particularly of large focal length, the most frequently suggested construction techniques have been to either mold a reflective facing layer and a holding layer into the desired shape, or to apply a reflective layer as a coating on a surface which has already been formed in the desired configuration.